A microemulsion is an oil-in-water or water-in-oil, transparent, thermodynamically stable dispersion of two or more immiscible liquids wherein the dispersed phase consists of small droplets with diameters in the range of about 10 to 100 millimicrons. Such microemulsions are known to enhance the efficacy of active compounds relative to equivalent levels of the same compound in a macroemulsion composition. See Skelton, P. R., Munk, B. H., and Collins, H. M., "Formulation of Pesticide Microemulsions", Pesticide Formulations and Application Systems; 8th Volume, ASTM STP 980, D. A. Hovde and G. B. Beestman, Eds., American Society for Testing and Materials, Philadelphia, (1988); U.S. Pat. No. 3,954,967; Canadian Patent No. 1,025,687; Prince, L., Microemulsions, Theory and Practice, Academic Press, (1977); and "Microemulsions-Properties Novel Chemistry BH Robinson, Chemistry in Britain 26 (1990), page 342.
Aqueous microemulsions of water-insoluble agriculturally active compounds generally exhibit good stability towards precipitation of the active compound at temperatures above about 10.degree. C. However, such compositions usually do not maintain the microemulsion state at temperatures below 10.degree. C., and, particularly, at the low temperatures of 2.degree.-3.degree. C. Ordinarily, such microemulsions become unstable, as evidenced by visible clouding of the otherwise transparent liquid as the temperature is decreased below about 10.degree. C., particularly at 2.degree.-3.degree. C.